As the two preceding patented inventions of Mr. Stephenson, in conjunction first with Mr. Dodd, and subsequently with Mr. Losh, were united to form oneloco motive engine, we could not well separate them. We must, however, now go back six months in our history, to place before the reader some account of a patent tFranted on the 6th of June, 1815, to that original thinker, " Richard Trevitluck, of Camborne, in Cornwall, engineer, for certain improvements in the high-pressure steam-engine, and the application thereof, with or without other machinery, to useful purposes." The specification contains several " scantlings of inventions" of a novel and ingenious nature, that are foreign to our present object ; we shall, therefore, omit these parts, and confine our extracts to those only that appertain to locomotion. After describing a curious specie& of motive engine, he observes, with respect to a peculiar part of it—" By putting flat plates or leaves upon die revolving arms within the case, I produce a cur rent of air in the manner of a winnowing machine to blow the fire : and I do sometimes place in the flue a screw, or a set of vanes, somewhat similar to the vanes of a smoke-jack, which screw, or vane, I do cause to revolve by con nexion with the steam-engine, for the purpose of creating an artificial draft in the chimney, always proportioned to the size of the fireplace and situation of the chimney. By either or both of these means, I obviate the necessity of a tall chimney, where the engine is used for portable purposes." Without insisting upon the perfect originality of the principles of this mechanism for exciting combustion, there appears to be novelty in the manner of applying them. But many of our readers will remember that a very few years ago a strongly con tested trial at law took place between Mr. Galloway and Lord Cochrane, on one part, and Messrs. Braithwaite and Erricson, on the other, to determine to which of the parties belonged very similar contrivances to the foregoing, which decidedly preceded them both.
The invention of tubular boilers, which are now so much employed in loco motion, is popularly considered to have emanated from Mr. Gurney; but the fact will be repeatedly shown in these pages, that he only rendered them the more complex by an additional twist. This remark is drawn from us upon reading Trevithick's specification of 1815, already quoted from. In the extract which we shall next make, it will be seen that lie, who was so many years prior to Gurney, did not pretend to be the inventor of tubular boilers, they being, in fact, made fifty years before him. lie claimed simply a peculiar modification of them in the words following :—" And I do further declare, that in order to make the boiler of a high pressure steam-engine of very light materials for portable purposes, and, at the same time, strong for resisting the pressure, as well as for exposing a large surface to the fire. I do construct the said boiler of a number of small perpendicular tubes, each tube closed at the bottom, but all opening at the top into a common reservoir, from whence they receive their water, and into which the steam of all the.tubes is united." In a recent Com mittee of the }louse of Commons on steam-carriages, it will he recollected, that some of the nimbus were led to believe, by the evidence of civil engineers, that all tubular boilers, or such as held their water in small distinct chambers, were modifications of " Gurney's principle." And the learned Dr. Lardner
considered that the peculiar merit of the Utter was the circumstance that every part of the boiler exposed to the action of the fire was filled with water. Those gentleman were of course unacquainted with the foregoing.
The great success which attended the improvements of the railway bars by Mesas. Lash and Stephenson, already described, seems to have stimulated rival manufacturers in the same undertaking; for we find that in the following year (1817) a patent was granted to Mr. John Hawke, of Gateshead, Durham, for "a new method of making iron rails, to be used in the construction of rail ways." The rails at that time in use, were, for the most part, cast iron ; and those which were of malleable iron were merely square or flat rolled bars, and were, consequently, as liable to be bent, as the cast were to be broken, by the heavy weights and concussions to which they were continually subjected. To obviate those defects, Mr. Hawks proposed to combine the properties of the two different kinds of iron, so that the combination should possess the rigidity of the cast metal against dead pressure, and the tenacity of the wrought to tie the cast metal together, should it become broken by percussion. The specification states that—" Instead of making the rails or bars of cast or malleable iron, as those now in use are, they are a compound of malleable and cast-iron, so con nected as to be stronger than if made of either kind alone. The surface is formed of cast iron, and the back, or under part, of malleable iron,joined together and formed when the metal of the former is in a fluid state ; and they become so inseparable that the cast iron may be broken at the nearest possible distances ; indeed, even inch by inch, which is scarcely possible to be occasioned by accident, and the rail will remain sufficient for the purposes of a railway ; at least, till it suits the convenience of the workmen to replace it, without inter ruption to the concern in which the railway may be used : and as a loss by a broken rail of this invention will be less than one in common use, the expense, although it may be a little more in the first instance, will be considerably less in the end, as the malleable iron may be used again, or as the old iron will be of much more intrinsic value than the other." The modes of combining cast and malleable iron together in the rails are various; but that which Mr. Hawks prefers, as affording the best security for their being firmly fixed together, is by running the cast iron, when in a state of fusion, on the malleable iron; to effect which the malleable part is to be first forged, or otherwise prepared in that form and of that strength which the nature of its intended purpose or appropriation points out as most proper. :That part of the malleable iron which is intended to be combined with the cast iron should be rendered rough and uneven by jagging or by perforation, by giving it a dovetailed form, or by any other means, so that the cast iron may firmly adhere thereto, without the liability of becoming loose by the violent action of the carriages. The malleable part must be clean, perfectly dry and warm, 'when laid in the mould to receive the melted iron, which should be poured in as soon as possible after the mould is ready to receive it, as any damp on the malleable iron will endanger the soundness of the cast iron part.